DESCRIPTION: The research proposed will examine the complex contingencies of mothers and infants interacting with each other in home settings during the first year of life. Adapting a dynamic systems approach of communication, the investigator hopes to refine the traditional approach to "maternal responsiveness" by considering both infant and mother behaviors simultaneously. Using 216 high-quality videotapes already made of 20-minute sessions of mother-infant interaction in naturalistic settings, the investigator expects to code the behaviors using a new approach for characterizing the interactions. The sample represents a diverse cross section of the population varying in maternal age, marital status, and SES. The aims are to: 1) examine the complex contingencies between the behaviors of mothers and infants during interaction by focusing on responsiveness of both dyad members, specificity of responses, latencies to respond to one another, and analysis of antecedent behaviors for each partner; and 2) study mutual adaptation during the sessions and longitudinally between ages 4 and 12 months. These analyses will evaluate interactional dominance as well as effects of context on mutual adaptation. The data analytic approach will use lag sequential methods as well as loglinear analyses to answer the questions posed.